Excited state intramolecular proton transfer in free base hemiporphyrazine

The photophysics of free base hemiporphyrazine has been studied by steady-state fluorescence and theoretical computations. The fluorescence spectrum shows two bands peaked at 420 and 675 nm, which, with the aid of theoretical computations, have been assigned to the emissions of two tautomers, differing for the position of the two central protons.